The field of this invention generally relates to packaging systems, and more particularly, relates to apparatus for forming a tight package from a bag having a product or substance disposed therein by tying or applying a closure to the bag in close proximity to the substance.
For marketing purposes, it has been found to be highly desirable to package products, and particularly produce, in a tight package. Consumer response to a product in a tight package is much more favorable than to the same quantity of product contained in a loose package.
Bag tying machines are well known in the art which include apparatus for forming a throat or neck in a bag proximate a product in the bag, and apparatus for applying a closure device, such as a wire, tape or clip, to the neck to secure the bag in a closed condition. Such bag tying apparatus often is not designed to provide for tightening of the bag around the product or depends upon an initial set-up and substantially uniform product size to achieve a tight bag. Typical of such prior art tying machines are the apparatus of U.S. Pat. Nos. 1,738,511, 2,711,278, 2,916,863, 3,919,829, 3,922,834 and 4,291,517.
Manually operable bag tying apparatus have been devised which will produce tight packages from bags having product therein. Such bag tying apparatus are formed to grip the bag near the end, form a throat or neck in the bag and pull the bag end until the neck is positioned immediately proximate the product, at which point a closure device is applied to the bag. Typical of manual bag tying apparatus which enable the formation of tight packages are the devices of U.S. Pat. Nos. 2,884,749 and 2,899,785.
Manual bag tying apparatus capable of forming tight packages, however, have been found to have several disadvantages which makes automation of the devices impractical. First, they often require tedious threading of the bag through a small opening. Additionally, securement of the bag to enable pulling of the neck down against the product also is tedious. Finally, such devices have relied upon the operator's touch and experience to establish how hard to pull on the bag.
Automation of bag tying apparatus which includes a tightening feature has met with limited success. U.S. Pat. No. 4,125,986 to Sheetz discloses a bagging apparatus with a weighing station, a bag loading station, a bag transfer station and a bag tying station. The amount of product to be packaged is determined by weight. The product is loaded into a bag which is gripped and suspended by fingers for transfer to a tying station. As the bag enters the tying station, the apparatus suspending the bag moves together to form a neck. The frame of the transfer station throws a switch, causing the tying machine to move downward a predetermined distance and then tie the bag.
The Sheetz apparatus is complex, and the apparatus for suspending and transferring the filled bag must be precisely adjusted. The tying operation occurs after the tying machine moves downward a predetermined distance toward the product within the bag; this distance must be adjusted by the operator in advance. Additionally, the Sheetz apparatus is not easy to retrofit into existing bagging systems.
U.S. Pat. No. 4,446,677 to Kokido discloses a packaging apparatus for producing a squeezed package. A predetermined amount of product is loaded into a bag. When the loading is completed, the weight of the product within the bag causes the product to narrow down to a throat above the product. This throat is positioned between a pair of fixed fingers; the throat is then further constricted by laterally closing a set of second fingers. Finally, the tying machine swings in from the side to apply a tie around the bunched throat.
The Kokido approach depends on an extremely complex arrangement of cams, gears and pushrods, requiring very precise tolerances in both manufacture and assembly. The relationship between the product in the bag and the tying machine is fixed; to obtain a tight package, the precisely correct quantity of product must be placed in the bag. Because the loading station and the tying station are integrated into one apparatus, the apparatus does not lend itself to being easily retrofitted into existing packaging assemblies. Also, the apparatus is not self adjusting during the tying process to accommodate product of varying size, for example, bundles of carrots of differing lengths.